INERTIAL SENSOR MODE TUNING CIRCUIT

• US 20130247668A1
• Filed: 09/20/2011
• Published: 09/26/2013
• Est. Priority Date: 09/20/2010
• Status: Abandoned Application

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Fairchild Semiconductor Corporation (ON Semiconductor Corporation)
• Inventors: Bryzek, Janusz
• Application Number:
  US13/821,619
• Publication Number:
  US 20130247668A1
• Time in Patent Office: Days
• US Class Current: 73/514.35
• CPC Class Codes: G01C 19/5776 Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38
• CPC Class Codes: G01P 15/08 with conversion into electric or magnetic values

Abstract

This document discusses, among other things, an mode matching circuit for a inertial sensor including an oscillator circuit configured to selectively couple to a sense axis of an inertial sensor and to provide sense frequency information of the sense axis, a frequency comparator configured to receive the sense frequency information of the sense axis and drive frequency information of the inertial sensor, and to provide frequency difference information to a processor, and a programmable bias source configured to apply a bias voltage to the sense axis to set a sense frequency of the sense axis in response to a command from the processor, and to maintain a desired frequency difference between the sense frequency and a drive frequency of the inertial sensor.

Claims

1. A mode matching circuit comprising:

an oscillator circuit configured to selectively couple to a sense axis of an inertial sensor and to provide sense frequency information of the sense axis;

a frequency comparator configured to receive the sense frequency information of the sense axis and drive frequency information of the inertial sensor, and to provide frequency difference information to a processor; and

a programmable bias source configured to apply a bias voltage to the sense axis to set a sense frequency of the sense axis in response to a command from the processor, and to maintain a desired frequency difference between the sense frequency and a drive frequency of the inertial sensor.

2. The mode matching circuit of claim 1, including a switch to couple the oscillator circuit to the sense axis.

3. The mode matching circuit of claim 1, including:

a second oscillator circuit configured to selectively couple to a second sense axis of the inertial sensor;

a second frequency comparator configured to receive an output of the second oscillator circuit indicative of a second sense frequency of the second sense axis and the drive frequency information, and to provide second frequency difference information to the processor; and

a second programmable bias source configured to apply a second bias voltage to the second sense axis to set the second sense frequency in response to a second command from the processor and to maintain a second desired frequency difference between the second sense frequency and the drive frequency of the inertial sensor.

4. The mode matching circuit of claim 1, including a drive circuit configured to provide kinetic energy to the inertial sensor and to provide the drive frequency information.

5. The mode matching circuit of claim 1, including a programmable drive resonator bias source configured to apply a drive bias to a drive resonator of the inertial sensor and to modulate the drive bias to adjust the desired frequency difference.

6. The mode matching circuit of claim 5 including a temperature sensor, wherein the is configured to maintain a desired drive frequency using the drive bias in response to temperature information received from the temperature sensor.

7. The mode matching circuit of claim 1, including a temperature sensor, wherein the programmable bias source is configure to maintain the desired frequency difference using the bias voltage in response to temperature information received from the temperature sensor.

8. A method comprising:

selectively coupling an oscillator circuit to a sense axis of an inertial sensor;

providing sense frequency information of the sense axis using the oscillator circuit;

receiving the sense frequency information and drive frequency information of the inertial sensor at a frequency comparator;

providing frequency difference information to a processor using the frequency comparator;

receiving a command from the processor at a programmable bias source;

applying a bias voltage to the sense axis to set a sense frequency of the sense axis; and

maintaining a desired frequency difference between the sense frequency and a drive frequency of the inertial sensor using the bias voltage.

9. The method of claim 8, wherein the selectively coupling the oscillator circuit to the sense axis includes actuating a switch.

10. The method of claim 8, including:

selectively coupling a second oscillator circuit to a second sense axis of the inertial sensor;

providing second sense frequency information of the second sense axis using the second oscillator circuit;

receiving the second sense frequency information and the drive frequency information of the inertial sensor at a second frequency comparator;

providing second frequency difference information to the processor using the second frequency comparator;

receiving a second command from the processor at a second programmable bias source;

applying a second bias voltage to the second sense axis to set a second sense frequency; and

maintaining a second desired frequency difference between the second sense frequency and the drive frequency of the inertial sensor using the second bias voltage.

11. The method of claim 8, including providing kinetic energy to the inertial sensor using a drive circuit.

12. The method of claim 11, including

receiving drive feedback information from the inertial sensor at the drive circuit;

and

providing the drive frequency information using the drive feedback information.

13. The method of claim 8, including:

applying a drive bias to a drive resonator of the inertial sensor; and

modulating the drive bias adjust the desired frequency difference.

14. The method of claim 13, including:

receiving temperature information from a temperature sensor; and

maintaining a desired drive frequency using the drive bias and the temperature information.

15. The method of claim 8, including:

receiving temperature information from a temperature sensor; and

maintaining the desired frequency difference using the bias voltage applied to the sense axis and the temperature information.

16. The method of claim 8, including providing a clock signal to the processor using the drive frequency information.

17. A system comprising:

an inertial sensor; and

a mode matching circuit including

an oscillator circuit configured to selectively couple to a sense axis of the inertial sensor and to provide sense frequency information of the sense axis;

a frequency comparator configured to receive the sense frequency information of the sense axis and drive frequency information of the inertial sensor, and to provide frequency difference information to a processor; and

a programmable bias source configured to apply a bias voltage to the sense axis to set a sense frequency of the sense axis in response to a command from the processor, and to maintain a desired frequency difference between the sense frequency and a drive frequency of the inertial sensor.

18. The system of claim 17, wherein the inertial sensor includes a microelectromechanical system (MEMS) inertial sensor.

19. The system of claim 17, wherein the inertial sensor includes a multi-axis inertial sensor.

20. The system of claim 17, wherein the inertial sensor includes a 3-axis MEMS gyroscope.